Added a proper (temporary) icon for the application.

Still working on the 16x16px one.
Finalized the 16x16 icon, yay!

After a lot of group discussion on the IRC, I've settled on the 4th one
seen here: http://i.imgur.com/1rGBV1m.png
Also made the 32x32 just a liiitle bit sharper.
Merge pull request #17 from rbndelrio/master

Added a proper (temporary) icon for the application.